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. 2025 Apr 9;37(4):e70037. doi: 10.1002/ajhb.70037

Delaying Motherhood—An Increasingly Common but Risky Trend in High‐Income Countries

Magdalena Kraus 1, Beda Hartmann 2, Sylvia Kirchengast 1,3,✉
PMCID: PMC11979679  PMID: 40200826

ABSTRACT

Objectives

Maternal age at first birth is increasing in most high‐income countries. The associations between advanced maternal age and perinatal complications, as well as newborn parameters, were analyzed using a dataset of 6831 singleton births among first‐time mothers taking place in Vienna, Austria, between 2010 and 2019.

Methods

In this single‐center medical records‐based retrospective study, the following obstetrical parameters have been included: conception mode, preterm birth (< 37th gestational week), labor induction, planned or emergency cesarean sections, adverse child presentation, newborn size, and Apgar scores. The outcomes of first‐time mothers older than 35 and 40 years, respectively, were compared to a reference group of first‐time mothers aged between 20 and 34 years.

Results

First‐time mothers aged 35 and older show a significantly (p < 0.009 resp. p < 0.001) higher risk of preterm births, with a 1.32‐fold risk for women between 35 and 39 years and a 2.35‐fold risk for women aged 40 and older. Maternal age is also significantly (p < 0.001) associated with an increased rate of medically induced labor, cesarean sections, and low‐weight newborns (< 2500 g). In contrast, there was no significant difference in Apgar scores among the newborns of different maternal age groups.

Conclusions

Advanced maternal age at first birth is a relevant risk factor for certain obstetric and neonatal complications. Delaying motherhood is a risky trend.

Keywords: breech presentation, cesarean section, delaying motherhood, late first‐time mothers, newborn size, pregnancy outcome, preterm birth

1. Introduction

At the beginning of the 20th century, women from the age of 26 years onwards were considered late first‐time mothers. In 1940, the cut‐off was raised to the age of 30 (Richter 1940). In 1958, the International Federation of Gynaecology and Obstetrics (FIGO) classified women who were 35 years or older at the birth of their first child as late first‐time mothers (Ritzinger et al. 2011), a definition that is still valid today. The reason for this was the increasing risk of miscarriage, fetal anomalies, stillbirths, and obstetric complications after the age of 35 (Sauer 2015), although some clinically relevant risks do not increase until the mother reaches the age of 40 (Ritzinger 2013).

In recent decades, the maternal age at first birth has increased steadily, particularly in high‐income countries (Ritzinger 2013). In Austria, the average age at first birth has risen over the last 40 years from 23.8 years in 1984 to 30.3 years in 2023 (Statistics Austria 2024).

There are many reasons for this trend. On the one hand, social and economic changes, such as new gender roles, the desire for self‐determination and professional success beyond the role of mother, longer periods of education, and more frequent employment for women, have led to fundamental changes in individual family planning. In Austria, for example, the proportion of women among university graduates rose from 41.9% in 1990 to 55.2% in 2022 (Statistics Austria 2024). On the other hand, political and economic crises, such as the global economic crisis in 2007, also led to a conscious decision to delay the start of reproduction (Molina‐García et al. 2019). These personal decisions were only possible thanks to the widespread availability of highly effective contraceptives with few side effects, as well as the increasingly successful options of assisted reproduction, which can fulfill a late desire to have children even at an advanced age (Ritzinger 2013; Findeklee and Diedrich 2022).

According to the classical theory of evolution, female life history was thus deliberately changed in high‐income countries. Delaying reproduction and thus late or very late motherhood represents a major risk for our ancestors but also for recent women living under poor conditions. The limited phase of reproductive capacity in female Homo sapiens , and the high neonatal and infant mortality rate made a rapid start to reproduction soon after reaching reproductive capacity an optimal strategy to ensure one's own reproductive success. The risk of dying early without offspring was too high, or of entering the phase of reduced fecundity if one waited too long, thus minimizing the prospect of offspring. Consequently, a fast life history was a successful strategy (Sýkorová and Flegr 2021; Last 2014; Sear 2020). Recently, the situation has dramatically changed in high‐income countries. The reduction of perinatal and neonatal mortality, advances in reproductive medicine, and the availability of safe contraceptives (Anderson and Johnston 2023) thus enable the best family planning on the one hand and reduce the risk of missing the possibility of successful reproduction due to the advancing biological clock on the other. Delaying reproduction is therefore the result of recent social and economic developments as well as advances in the medical field (Dorn 2012; Zabak et al. 2023).

Nevertheless, late pregnancies and births are viewed critically as they also increase risks for the mother and the newborn (Ogawa et al. 2017). These include an increased risk of aneuploidy, chromosomal aberrations such as trisomy 21 (Frick 2021), increased miscarriage and premature birth rates (Sauer 2015), and an increased risk of cesarean section (Fitzpatrick et al. 2016; Mylonas and Friese 2015; Sydsjö et al. 2019; Frick 2021). The probability of giving birth to a small for gestational age (SGA) child is also higher for late‐term mothers than for younger mothers (Sydsjö et al. 2019; Ratiu et al. 2023). According to Berger et al. (2021), women as young as 35 are significantly more likely to have a premature birth or a low–weight baby. Fetal growth restriction can be caused by chronic diseases of the mother, such as hypertension, diabetes, or kidney disease, but also by chromosomal diseases, infections, or placenta previa, all factors that become more frequent with increasing maternal age (Pelikan and Hodel 2014; Glick et al. 2021).

The trend towards late motherhood therefore also harbors risks that are also relevant for public health and health policy (Ritzinger et al. 2011).

The present study aimed to analyze the significance of delaying reproduction for gestation duration, fetal growth, and vital function of the newborn as well as the birth outcome in an Austrian sample. Austria is interesting for this question because the care of pregnant women has been regulated by the mother–child pass since the 1970s and pregnant women thus receive optimal medical care up to and including childbirth. First‐time mothers over the age of 35 are also considered high‐risk pregnant women and receive special care. The pregnancy outcome of these women in Austria is therefore of particular interest. The following two hypotheses were tested:

  1. First‐time mothers between 35 and 39 years and 40 years and older have a higher risk than 20‐ to 34‐year‐old first‐time mothers for preterm birth and fetal growth restriction.

  2. First‐time mothers between 35 and 39 years of age and 40 years of age and older have a higher risk of perinatal problems than 20‐ to 34‐year‐old first‐time mothers.

2. Material and Methods

2.1. Dataset

The original data set of this single‐center medical record‐based retrospective study included 15,405 individual births that took place at Clinic Donaustadt between 2010 and 2020. Clinic Donaustadt is one of the largest public maternity clinics in Vienna. All parameters analyzed in the study were collected and documented during standard medical check‐ups during pregnancy and birth. The following inclusion criteria were defined to be included in the final data set of this study: Single birth, live birth, maternal age of at least 20 years. Strict exclusion criteria were as follows: Stillbirths as well as multiple pregnancies, as these pose an increased risk of preterm birth and fetal growth restriction regardless of maternal age (Laine et al. 2019; Tingleff et al. 2023). In addition, maternal age of less than 20 years was a strict reason for exclusion. The strict exclusion of mothers younger than 20 years was due to the increased risks during pregnancy and birth in adolescent mothers described by several authors (Demirci et al. 2016; Li et al. 2023). Although it cannot be assumed for Austria that the pregnancy outcome is significantly reduced in mothers aged 18–20, we decided to include only mothers aged 20 and over in the study. Therefore, 257 mothers under the age of 20 were excluded. One case was excluded because the mother reported 14 unsuccessful previous pregnancies, which might be a pathological case. The final sample comprised 6831 first‐time mothers aged 20–51 years (x = 29.4 ± 5.3 years). The rate of first‐time mothers was 46.1% in the original dataset. The study was conducted according to the guidelines of the Declaration of Helsinki and approved by the Ethics Committee of Vienna (responsible for Public Hospitals) (Protocol number: EK 19‐274‐VK 18 March 2020).

2.2. Maternal Parameters

At the first prenatal check‐up (usually in the 8th week of pregnancy), a thorough medical anamnesis was taken with regard to acute, past, and chronic illnesses, previous pregnancies, and medication intake. Nicotine consumption during pregnancy was also asked about. Maternal body height was determined using a standard anthropometer by trained clinic staff. Prepregnancy weight was obtained by an interview using the retrospective method during the first prenatal visit (usually at the 8th to 10th week of gestation). In addition, body weight was measured to the nearest 0.1 kg using a digital scale at this first prenatal visit. The mean value of the self‐reported and the measured body weight at the 8th to 10th gestational week was calculated. Since only an extremely small weight gain of about 1.7% is assumed for the first trimester of pregnancy (Gueri et al. 1982), prepregnancy week was determined by the calculation of the mean value of self‐reported and measured body weight at the prenatal visit. Prepregnancy weight status was determined by calculation of the body mass index (BMI) (kg/m2). Four weight status categories were determined: underweight (BMI ≤ 18.5 kg/m2), normal‐weight (18.5–24.99 kg/m2), overweight (25.0–29.99 kg/m2), and obese (≥ 30.0 kg/m2) (World Health Organisation 2000).

Additionally, maternal body weight was measured before delivery (= at the end of pregnancy). The weight gain during pregnancy was calculated by subtracting prepregnancy weight from body weight before delivery.

To define late motherhood and very late motherhood, the women were assigned to three age groups. Late motherhood was defined as maternal age between 35 and 39 years (n = 973). Very late motherhood was defined as a maternal age of 40 years and over (n = 242).

Women who had given birth for the first time between the ages of 20 and 34 were defined as the control or reference group (n = 5617).

2.3. Obstetrical Parameters

The following obstetric characteristics were recorded: Conception mode spontaneous versus Assisted Reproductive Technologies (ART) such as In Vitro‐fertilization, Intracytoplasmatic Sperm Injection (ICSI), Homologic or Heterologic Insemination, or Hormonal Stimulation. Concerning childbirth, induction of labor with medication and the mode of delivery, that is, spontaneous vaginal delivery, vacuum extraction, planned cesarean section, and unplanned or emergency cesarean section were documented. All planned cesarean sections were carried out exclusively for medical reasons. Cesarean sections upon maternal request without any medical indication were not performed at the Clinic Donaustadt. The most frequent indications for emergency cesarean delivery were fetal distress and obstructed labor. A delivery date before the 37th week of pregnancy is defined as preterm birth.

2.4. Newborn Parameters

The newborns were weighed and measured immediately after birth by an experienced midwife. The birth weight was determined in grams using a digital infant scale and categorized accordingly into four weight categories as follows: < 1500 g (very low birth weight), 1500–2499 g (low birthweight), 2500–3999 g (normal weight), and ≥ 4000 g (macrosomic) (Araujo Júnior et al. 2017). Birth length was measured in cm using a standard measurement board for infants, and head circumference (in cm) using a standard tape. Newborn vital function was determined by the APGAR scores recorded at 1, 5, and 10 min after birth (Apgar 1953, Schmidt et al. 1988; Hoppen 2016; Simon et al. 2024).

The newborn sex was recorded. A total of 51% of the newborns were male and 49% female. This sex distribution corresponds to the usual sex ratio at birth (Grech 2023).

2.5. Statistical Analysis

All statistical analyses were performed using IBM SPSS Version 27. After computing descriptive statistics (absolute and relative frequencies, means, standard deviations, medians, range), Student t tests, Chi‐squares, and Fisher exact tests were performed to test group differences for their statistical significance. Linear multiple regression analyses and binary logistic regression analyses were calculated to test the association patterns between maternal age and newborn size as well as obstetrical parameters. Odds ratios were used to quantify the risk of delayed and very delayed first motherhood for low birth weight, the need for labor induction, cesarean section, and preterm birth. The significance level is set to p < 0.05.

3. Results

3.1. Sample Description

Table 1 presents the sample characteristics of 6831 first‐time mothers and their newborns. The average maternal age was 29.4 years, with the oldest mother being 51 years old. Most mothers (79.2%) were between 20 and 34 years old and thus represented the reference group for further analysis. To the definition of late first‐time mothers aged 35 to 39 corresponded 13.7% of the mothers, and only 3.4% were very late first‐time mothers aged 40 and over.

TABLE 1.

Sample characteristics—maternal and newborn parameters of 6831 first birth in Clinic Donaustadt (Vienna, Austria) between 2010 and 2019.

Parameters x (SD) Min‐max
Maternal characteristics
Age (in years) 29.4 (5.3) 20–51
Maternal age groups
20–34 years 79.2%
35–39 years 13.7%
≥ 40 years 3.4%
Body height (in cm) 165.8 (6.3) 140–193
Prepregnancy weight (in kg) 64.8 (13.9) 36.0–160.0
Weight at the end of pregnancy (in kg) 79.8 (14.5) 44.0–170.0
Gestational weight gain (in kg) 15.2 (5.8) −15.0 – 43.0
Prepregnancy BMI (kg/m2) 23.53 (4.74) 13.39–57.37
< 18.50 kg/m2 6.8%
18.50–24.99 kg/m2 65.8%
25.00–29.99 kg/m2 17.4%
30.00–39.99 kg/m2 8.9%
≥ 40.00 kg/m2 1.1%
Number of previous pregnancies 1.3 (0.7) 1–6
Smoking during pregnancy 12.5%
Newborn characteristics
Newborn sex
Male 51.0%
Female 49.0%
Birth length (in cm) 50.4 (2.7) 28.0–65.0
Head circumference (in cm) 33.9 (1.7) 21.5–50.0
Birthweight (in g) 3315.1 (540.5) 470–5350
< 1500 g 0.8%
1500–2499 g 5.1%
2500–3999 g 86.1%
≥ 4000 g 8.0%
APGAR score after 1 min 8.95 (1.12) 1–10
APGAR score after 5 min 9.72 (0.79) 1–10
APGAR score after 10 min 9.91 (0.45) 2–10
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Most of the women (65.8%) met the definition of normal weight. About 17% of the women were overweight, and only 10% were obese. More than 86% of the newborns were of normal weight; 8% weighed 4000 g and more. Less than 1% were extremely light, with a birth weight below 1500 g. About 5% corresponded to the definition of low weight, with a weight between 1500 and 2500 g. The mean number of previous pregnancies was 1.3, with one woman reporting 15 unsuccessful pregnancies (see Table 1).

Table 2 demonstrates the obstetrical parameters. The births took place between the 26th and 42nd gestational week, whereby 7.1% of the newborns were born before the 37th week and are therefore classified as preterm births. More than 90% of conceptions were spontaneous, and only 3.3% occurred after IVF, and only 1.5% after ICSI.

TABLE 2.

Sample description of obstetrical parameters of 6831 first births in Clinic Donaustadt (Vienna, Austria) between 2010 and 2019.

Obstetrical parameters x (SD) % Min‐max
Umbilical cord blood pH value 7.23 (0.08) 6.82–7.71
Gestational week of birth 39.1 (1.9) 26–42
Preterm birth < 37 gestational week 7.1%
Conception mode
Spontaneously 91.9%
In vitro fertilization (IVF) 3.3%
Intracytoplasmatic sperm injection (ICSI) 1.5%
Heterologic insemination 0.0%
Homologic insemination 0.1%
Hormonal stimulation 0.7%
Labor induction 27.4%
Child presentation
Head presentation 92.5%
Breech presentation 6.8%
Transverse presentation 0.2%
Birth mode
Spontaneous 73.8%
Vacuum extraction 9.5%
Planned CS 5.6%
Emergency CS 11.1%
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Abbreviation: CS = cesarean section.

Almost 7% of the newborns had a breech presentation at birth. The birth itself was induced with medication in 27.4%. Almost 10% required a vacuum extraction, and in 5.6% a planned cesarean section was performed. An emergency cesarean section was necessary in 11% of cases.

3.2. Comparison of Maternal and Newborn Characteristics Between the Three Maternal Age Groups

The late and very late first‐time mothers were significantly taller and significantly heavier before pregnancy. Weight gain during pregnancy, on the other hand, was significantly lower (p < 0.001) in both mothers aged 35–39 years and mothers aged 40 years and older than in the reference group. The number of previous pregnancies was significantly lowest in the reference group (see Table 3). The newborns of the late and very late first‐time mothers were significantly lighter, shorter, and had a significantly smaller head circumference than the newborns of the reference group. They were also born significantly earlier. However, as far as vital functions after birth were concerned, no significant differences were found between late or very late first‐time mothers and the reference group (see Table 3).

TABLE 3.

Maternal and newborn characteristics according to maternal age group of 6831 first birth in Clinic Donaustadt (Vienna, Austria) between 2010 and 2019.

Somatic parameter Reference group Maternal age groups
20–34 years 35–39 years ≥ 40 years
Mean (SD) Mean (SD) p Mean (SD) p
Maternal characteristics
Body height (cm) 165.6 (6.3) 167.0 (6.4) < 0.001 167.1 (6.6) < 0.001
Prepregnancy body weight (kg) 64.4 (13.9) 66.3 (13.6) < 0.001 68.2 (15.4) < 0.001
End of pregnancy body weight (kg) 79.7 (14.5) 80.8 (13.9) 0.034 80.6 (15.5) 0.173
Gestational weight gain (kg) 15.4 (5.8) 14.5 (5.4) < 0.001 12.7 (4.9) < 0.001
Body mass index kg/m2 23.46 (4.75) 23.73 (4.57) 0.049 24.38 (5.06) 0.002
Number of pregnancies 1.3 (0.6) 1.5 (0.9) 0.023 1.8 (1.1) < 0.001
Newborn characteristics
Gestational week 39.2 (1.8) 38.9 (2.0) 0.003 38.4 (2.9) < 0.001
Birthweight (g) 3331 (527) 3267 (559) < 0.001 3129 (688) < 0.001
Birth length (cm) 50.5 (2.6) 50.3 (2.7) 0.007 49.6 (3.7) < 0.001
Head circumference (cm) 34.0 (1.7) 33.8 (1.7) < 0.001 33.6 (2.3) < 0.001
APGAR (1 min) 8.95 (1.09) 8.89 (1.26) 0.060 8.99 (0.94) 0.293
APGAR (5 min) 9.73 (0.70) 9.64 (0.79) 0.084 9.76 (0.79) 0.273
APGAR (10 min) 0.92 (0.44) 9.88 (0.57) 0.010 9.89 (0.37) 0.180
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Note: Student's t tests.

3.3. Comparison of Obstetrical Parameters Between the Three Maternal Age Groups

As demonstrated in Table 4, late and very late first‐time mothers were highly significantly more likely to need ART to get pregnant. Among mothers aged 35–39 years, ART frequency was almost three times higher than in the reference group; among very late first‐time mothers, over 30% needed ART. This corresponds to a 7‐fold increased risk compared to the reference group. Furthermore, compared to the reference group, late first‐time mothers were significantly more likely to require induction of labor, were significantly more likely to have a preterm birth, breech presentation, but also had a significantly increased risk of requiring a planned cesarean section or an emergency cesarean section. The very late first‐time mothers have a significantly higher risk of premature birth, induction of labor, planned and emergency cesarean sections, as well as newborns with very low (< 1500 g) and low birth weight (< 2500 g) than first‐time mothers aged 20–34 years. There was no significant association between maternal age groups and the risk of giving birth to a macrosome newborn (≥ 4000 g). (see Table 4).

TABLE 4.

Obstetrical relevant parameters according to maternal age group of 6831 first birth in Clinic Donaustadt (Vienna, Austria) between 2010 and 2019.

Obstetrical relevant parameter Reference group Maternal age groups
20–34 years 35–39 years ≥ 40 years
n (%) n (%) OR p n (%) OR p
ART 330 (5.9%) 147 (15.1%) 2.85 < 0.001 15 (31.0%) 7.19 < 0.001
Preterm birth 366 (6.5%) 82 (8.4%) 1.32 0.019 34 (14.0%) 2.35 < 0.001
Labor induction 1481 (26.4%) 299 (30.7%) 1.19 0.003 92 (38.0%) 1.67 < 0.001
Breech presentation 362 (6.5%) 86 (8.5%) 1.41 0.004 17 (7.1%) 1.10 0.389
Planned CS 286 (6.3%) 75 (10.3%) 1.71 < 0.001 20 (12.0%) 2.01 0.005
Emergency CS 570 (11.8%) 139 (17.6%) 1.59 < 0.001 51 (25.8%) 2.58 < 0.001
BW < 1500 g 37 (0.8%) 8 (1.0%) 1.28 0.321 10 (4.8%) 6.67 < 0.001
BW < 2500 g 297 (5.8%) 74 (8.3%) 1.48 0.003 33 (14.3%) 2.74 < 0.001
BW < 4000 g 455 (8.1%) 79 (8.1%) 1.00 0.984 12 (5.0%) 0.59 0.077
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Note: Chi‐squares, Fisher‐exact‐test, and odds ratios (OR).

Abbreviations: ART = artificial reproductive technologies, BW = Birth weight, CS = cesarean section.

The associations of maternal age with newborn size were corrected for maternal height, gestational weight gain, nicotine consumption, gestational week of birth, and prepregnancy BMI using linear regression analyses. The birth weight and head circumference of the newborn were significantly negatively associated with the mother's age, independent of the other parameters (see Table 5).

TABLE 5.

Association patterns between maternal age and newborn size of 6831 first birth in Clinic Donaustadt (Vienna, Austria) between 2010 and 2019.

Maternal parameters Dependent parameters: newborn size
Birthweight Birth length Head circumference
R 2 B p R 2 B p R 2 B p
Maternal age 0.467 −3.94 < 0.001 0.435 −0.01 0.051 0.341 −0.01 0.048
Body height 11.69 < 0.001 0.05 < 0.001 0.04 < 0.001
Gestational weight gain 14.13 < 0.001 0.05 < 0.001 0.03 < 0.001
Smoking −177.85 < 0.001 −0.68 < 0.001 −0.47 < 0.001
Gestational week 176.84 < 0.001 0.87 < 0.001 0.49 < 0.001
Prepregnancy BMI 12.69 < 0.001 0.04 < 0.001 0.02 < 0.001
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Note: Multiple linear regression analyses; B = Regression coefficient.

According to the results of the binary logistic regression analyses, maternal age was also significantly associated with the obstetric parameters, independently of maternal height, weight gain during pregnancy, nicotine consumption, duration of pregnancy, and weight status. Maternal age significantly increases the risk of premature birth, induction of labor with medication, low birth weight, breech presentation, and planned and emergency cesarean section (see Table 6).

TABLE 6.

Associations between maternal age and obstetrical parameters (binary logistic regression analyses) of 6831 first birth in Clinic Donaustadt (Vienna, Austria) between 2010 and 2019.

Dependent obstetrical parameter
Maternal parameters Preterm birth (< 37 SSW) Labor induction BW < 2500 g
B p Exp(B) B p Exp(B) B p Exp(B)
Maternal age 0.04 < 0.001 1.04 0.03 < 0.001 1.03 0.01 0.343 1.01
Body height −0.02 0.012 0.98 −0.01 0.074 0.99 −0.03 0.023 0.97
Weight gain −0.05 < 0.001 0.95 0.01 0.072 1.01 −0.03 0.011 0.97
Smoking 0.41 0.005 1.50 0.05 0.580 1.05 0.78 < 0.001 2.17
Gestational week — — — 0.08 < 0.001 1.08 −0.98 < 0.001 0.34
Prepregnancy BMI 0.01 0.923 1.00 0.06 < 0.001 1.06 −0.04 0.017 0.96
Breech presentation Planned CS Emergency CS
B p Exp(B) B p Exp(B) B p Exp(B)
Maternal age 0.04 < 0.001 1.04 0.04 < 0.001 1.05 0.07 < 0.001 1.08
Body height 0.01 0.411 1.01 0.01 0.628 1.00 −0.05 < 0.001 0.95
Weight gain 0.04 < 0.001 1.04 0.05 < 0.001 1.05 0.05 < 0.001 1.05
Smoking −0.34 0.051 0.72 −0.33 0.078 0.71 −0.18 0.191 0.84
Gestational week −0.26 < 0.001 0.77 −0.34 < 0.001 0.72 −0.05 0.021 0.95
Prepregnancy BMI −0.01 0.511 0.99 0.02 0.055 1.02 0.07 < 0.001 1.07
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Note: Term birth = 0, preterm birth =1; no labor induction = 0, labor induction = 1; birthweight > 2500 g = 0, < 2500 g = 1; head presentation = 0, breech presentation = 1; spontaneous birth = 0, planned CS = 1; spontaneous birth = 0, emergency CS = 1.

Abbreviations: BMI = body mass index, CS = cesarean section.

4. Discussion

This study tested two hypotheses. First, it was predicted that first‐time mothers aged 35–39 years and 40 years and older were at higher risk than 20–34‐year‐old first‐time mothers for preterm birth and fetal growth restriction. Secondly, it was examined whether first‐time mothers of advanced maternal age (AMA) were at higher risk of labor difficulties. Both hypotheses were largely confirmed, despite the good medical care provided to late first‐time mothers in Austria.

The pregnancies of late first‐time and very late first‐time mothers were shorter than those of the reference group. The adjusted odds ratios (aORs) showed a 1.32‐fold risk of preterm birth for 35‐ to 39‐year‐olds and even a 2.35‐fold risk for women aged 40 and over. Binary logistic regressions also showed that the relative probability of preterm birth increased by 4% with each one‐year increase in maternal age and that this association was highly significant. This corresponds to the results of Waldenström et al. (2017), which also show that advanced as well as very AMA increased the risk of spontaneous as well as medically induced preterm birth. Fuchs et al. (2018) also showed in their Canadian study that a pregnancy from the age of 40 increased the risk of spontaneous preterm birth by 1.2 times compared to pregnancies between the ages of 30 and 34. The higher frequency of preterm births in older mothers could be due to a higher rate of pregnancy complications, such as premature rupture of membranes, placental dysfunction with or without pre‐eclampsia, and intrauterine growth retardation (Ratiu et al. 2023; Restrepo‐Méndez et al. 2015). The occurrence of placental abnormalities could also explain the increased risk of preeclampsia in older mothers and possibly lead to premature induction of labor. Another possible reason for the higher preterm birth rate in older mothers is a progesterone deficiency (Glick et al. 2021).

There was also a clear statistical correlation between maternal age and newborn size. Mothers in the oldest group gave birth to the lightest and smallest newborns. The risk of having a newborn with a low or very low birth weight was increased 2.74‐fold and 6.67‐fold, respectively, for first‐time mothers aged 40 and over. For late‐term mothers between 35 and 39 years of age, the risk of a newborn with a low or very low birth weight increased 1.48‐fold and 1.28‐fold, respectively. This result also corresponds to that of Sydsjö et al. (2019), according to whom mothers aged 40 and over were twice as likely to have a child with a low birth weight than mothers under 40. According to this study, the risk of low birth length was also increased in mothers older than 40. The study by Berger et al. (2021) produced similar results. Here, mothers over the age of 35 showed a significantly increased risk of premature birth and low birth weight. Molina‐García et al. (2019), on the other hand, found no significant difference between late‐term and younger mothers. The fact that the newborns of older mothers were lighter, shorter, and had a smaller head circumference seems surprising, as in our sample both the mothers aged 35 to 39 and 40 and over were on average 1.4 cm taller than the mothers in the reference group and thus significantly taller. Taller mothers tend to have taller newborns (Morkuniene et al. 2022). The greater body height of older first‐time mothers in our study can be explained by the fact that late first‐time mothers in Austria have a significantly higher socioeconomic status and are significantly more likely to have a higher level of education than younger mothers (Statistik Austria 2024). There is also a significant association between body height and education level documented for men in Austria (Waldhör et al. 2023). The higher the level of education, the higher the body height. The differences in mean body heights between late first‐time mothers and the reference group are not due to the general acceleration process or differences in the ethnic background of the mothers; the differences in body height are due to different socioeconomic and educational levels of the mothers. In the present study, however, the taller body height of older mothers cannot exert its positive influence on the fetal growth process; AMA appears to have a negative effect on the fetal growth process that is independent of maternal body height. This is also reflected in the results of the regression analyses in the present study, which clearly show a significant negative effect of maternal age on the fetal growth process independent of the positive effects of maternal height, gestational weight gain, and prepregnancy weight status.

The first hypothesis of this study, that late‐term mothers have a higher risk of preterm birth and fetal growth restriction, could therefore be confirmed.

As far as vital signs after birth were concerned, no significant differences in APGAR scores at 1 and 5 min after birth were observed between the late‐term and very late‐term mothers and the reference group. Only the APGAR scores after 10 min were significantly lower in the late‐term mothers than in the reference group. This corresponds to the results of the studies by Yogev et al. (2010) and Ratiu et al. (2023), but is in contrast to the results of Bianco et al. (1996), Jolly et al. (2000), and Traisrisilp and Tongsong (2015), who described lower APGAR scores in older mothers.

The second hypothesis, that first‐time mothers of AMA have a higher risk of birth problems, was also confirmed. Late‐term and very late‐term mothers showed a significantly higher risk of the need for induction of labor with medication, a breech presentation, the need for a planned cesarean section, and an emergency cesarean section. For women aged 35–39 years, the risk of induction of labor with medication was 1.19 times higher. For mothers aged 40 and over, the risk increased 1.67‐fold compared to the reference group. This is in line with the findings of Jacobsson et al. (2004), who reported a 1.75‐fold increased risk of the need for induction of labor with medication in mothers between 40 and 44 years of age compared to 20‐ to 29‐year‐old mothers. Ecker et al. (2001) also report a significant positive correlation between maternal age and induction of labor with medication.

In our study, we also observed a significantly increased risk of breech presentation in older mothers. This is also described by Noli et al. (2019). Dildy et al. (1996) and Jolly et al. (2000) also report an increased number of breech deliveries in women of advanced age. Jolly et al. (2000) found odds ratios (ORs) of 1.37 for pelvic presentation in women aged between 35 and 40 and odds ratios of 1.72 in women aged 40 and over. Dildy et al. (1996) reported a pelvic presentation incidence of 11% in women over 45 years of age. This increased incidence of pelvic presentation may be due to higher rates of uterine leiomyomas and uterine anomalies with age, as well as age‐related skeletal muscle deterioration (Ratiu et al. 2023). However, Ratiu et al. (2023) Wang et al. (2011) and Elser and Selbmann (1982) found no significant differences in fetal position, especially pelvic presentation, between younger and older primiparous women. According to Elser and Selbmann (1982), there is no significantly increased risk of breech presentation for mothers aged 40 and over. However, this result could be a sampling artifact, as the proportion of mothers over 40 in this study was extremely low.

Regarding the mode of delivery, our results confirm the assumption that the number of spontaneous vaginal births decreases with increasing age of first‐time mothers. AMA was identified as an independent risk factor for planned cesarean sections and emergency cesarean sections. Mothers between 35 and 39 years had a highly significant higher risk of planned cesarean section (aORs = 1.71) and emergency cesarean section (aORs = 1.59). From a maternal age of 40 years and older, the risk of a planned cesarean section was significantly increased by a factor of 2.01 and for an emergency cesarean section by a highly significant factor of 2.58. In a British study of 385 120 singleton pregnancies, it was found that women between 35 and 39 years of age had a higher risk of planned cesarean section (aORs = 1.77) and emergency cesarean section (aORs = 1.59) compared to the reference group of 18‐ to 34‐year‐old women (Jolly et al. 2000). According to the results of Jolly et al. (2000), the risk for mothers aged 40 and over already increased 2.17‐fold for a planned cesarean section and 2.67‐fold for an emergency cesarean section. First‐time mothers aged 45 and over were already eight times more likely to have a cesarean section compared to younger first‐time mothers (Carolan et al. 2013).

AMA is associated with an increase in placental dysfunction, fetal miscarriage, previous cesarean sections, and multiple pregnancies, which are considered to predispose to cesarean section. Several studies explain the decline in myometrial function with age as a factor in the increasing rate of cesarean sections in older mothers (Ratiu et al. 2023). Cleary‐Goldman et al. (2005) reported a decrease in the effectiveness of myometrial gap junctions as well as a decrease in the number and sensitivity of myometrial oxytocin receptors, which may impair labor. Roustaei et al. (2018) indicated reduced uterine blood flow associated with increased uteroplacental blood flow at older ages, which may increase the risk of hemorrhage during and after labor and necessitate a cesarean section.

Looking at the results of this study from an evolutionary perspective, delaying reproduction, that is, a very slow life history, appears to be a disadvantage. Women who do not start reproducing until the end of the reproductive span not only run the risk of fertilization failure, but even after successful fertilization, the probability of successful reproduction is reduced. Prematurity and low birth weight increase neonatal and infant mortality (Jana et al. 2023), but also increase the risk of morbidity, which can have both short‐ and long‐term negative effects (Morkuniene et al. 2025). An increased rate of breech deliveries can make vaginal birth impossible and thus increase maternal mortality (Ekéus et al. 2019). Obstetric measures such as induction of labor and planned and emergency cesarean sections are also very recent measures. For our ancestors, a slow life history pattern characterized by delaying reproduction would have been a highly risky undertaking (Sear 2020). The adverse effects of late reproduction might be interpreted as a hint of adaptiveness of human menopause (Pavard et al. 2008; Pelikan and Hodel 2014; Hawkes et al. 1998). The current trend toward late motherhood is only a viable option under current conditions. For our ancestors, fast patterns of life history were more promising.

5. Conclusion

Even under very good medical and social conditions, delaying motherhood is associated with increased risks and justifies the classification of late‐term mothers as high‐risk pregnant women. These increased risks will not reverse the trend towards ever‐later motherhood and could therefore also have a considerable influence on health policy. From an evolutionary perspective, the trend toward slow life history patterns also appears to be a cause for concern.

6. Limitation

The present study has certain limitations such as the limited availability of other important parameters. Only parameters that were documented as standard during the medical check‐ups could be included in this medical record‐based reproductive single center study. This means that behavioral and lifestyle parameters such as diet, physical activity, and information on socioeconomic status were not available. Generalizations of the results should also be viewed with caution, as the study examined a homogeneous group of late first‐time mothers in Austria. Comparisons with other studies should therefore be interpreted with caution. A further limitation is that the number of late mothers aged 40 and over (3.4%) is low, although the sample of 6832 cases can be considered representative. The sizes of the individual maternal age groups vary. It was to be expected that the group of pregnant women aged between 20 and 34 years (79.2%) was the largest. In contrast, the groups of mothers aged between 35 and 39 and aged 40 and over were smaller.

Author Contributions

M.K. designed the study, drafted the manuscript. B.H. designed the study and collected the data. S.K. designed the study, analyzed the data, drafted the manuscript.

Conflicts of Interest

The authors declare no conflicts of interest.

Data Availability Statement

The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions.

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Associated Data

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Data Availability Statement

The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions.

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